Throughout the world, women bear the burden of sexually transmitted infections (STI) and HIV. An interdisciplinary approach that includes obstetrician-gynecologist clinician-researchers, bench and social scientists is needed to investigate the biological, cultural, behavioral and socioeconomic causes for these burgeoning pandemics. The purpose of the proposed grant is to train a group of obstetrician-gynecologists and PhD researchers in reproductive infectious disease (RID) with emphasis on the study of STIs and HIV. The RID fellowship is led by one of the most comprehensive academic departments of obstetrics and gynecology in the U.S. The Principal Investigator (PI), Dr. Nancy Padian has led single and multi-site clinical trials and observational studies for STI and HIV prevention among women domestically for over 20 years and internationally for over a decade. The Co-Director, Dr. Craig Cohen, has performed groundbreaking studies in prevention, etiology and treatment of STIs and HIV care and prevention internationally, and was recently awarded the STI Clinical Trials Group contract (NIAID HHSN266200400074C) to conduct STI diagnostic, therapeutic, vaccine and microbicide trials worldwide. Both Co-Directors and mentors have established successful records training fellows, and students. The program aspires to select two fellows per year for a three to four year program that when fully operational will support six to seven fellows, approximately four to five obstetrician-gynecologists, and one to two PhDs from an RID related field. The Department of Obstetrics Gynecology and Reproductive Sciences at UCSF along with partner institutions UC Berkeley, Gladstone Institute of Virology and Immunology, SF Department of Public Health, and STD Control Branch of the California Department of Health Services provides an excellent home for the RID fellowship program. The program will provide trainees with the tools and experience necessary to develop into independent investigators in the field of RID. To accomplish this goal, the program will provide trainees with: (i) academic training including a Masters in Public Health or other relevant field (e.g., Virology, Molecular Biology);(ii) opportunity to conduct all phases of research;(iii) professional development training and support;(iv) a strong mentored relationship;(v) international research experience in close collaboration with international investigators;(vi) planning for the transition to become an independent investigator;and (vii) for physicians, six months of clinical training, and for PhDs broad exposure to the clinical management of RID. We plan to launch fellows into productive careers in RID research and thus to continue the UCSF tradition of international leadership in infectious disease research and training.